Phyla Lour.
Phyla is a taxonomically complex genus of 5 species (Marx & al. 2010; ca. 11 according to Mabberley 2008), all initially confined to the tropical and warm-temperate regions of the world. One variable species is cultivated as an ornamental (for ground cover) (see Akeroyd 2000, Jäger & al. 2008). It also occurs as an environmental weed outside its native distribution range.
The generic limits of Phyla are still somewhat uncertain. It is obviously closely related to Lippia L. and Lantana L. (Marx & al. 2010). Tutin (1972) still accepted Phyla in a broadly circumscribed genus Lippia.
Literature:
Akeroyd J.R. (2000) Phyla. In: Cullen J. & al. (eds.), The European Garden Flora, vol. 6. Cambridge University Press, Cambridge: 155.
Jäger E.J., Ebel F., Hanelt P. & Müller G. (eds.) (2008) Rothmaler Band 5. Exkursionsflora von Deutschland. Krautige Zier- und Nutzpflanzen. Springer Verlag, Berlin: 880 p.
Mabberley D.J. (2008) Mabberley’s plant-book (3th ed.). Cambridge University Press, Cambridge: XVIII + 1021 p.
Marx H.E., O'Leary N., Yuan Y.-W., Lu-Irving P., Tank D.C., Mulgura M.E. & Olmstead R.G. (2010) A molecular phylogeny and classification of Verbenaceae. Am. J. Bot. 97(10): 1647-1663. [available online at: http://depts.washington.edu/phylo/OlmsteadPubs/Marx_et_al_2010.pdf].
Munir A.A. (1993) A taxonomic revision of the genus Phyla Lour. (Verbenaceae) in Australia. J. Adelaide Bot. Gard. 15(2): 109-128.
O’Leary N. & Múlgura M.E. (2012) A taxonomic revision of the genus Phyla (Verbenaceae). Ann. Missouri Bot. Gard. 98: 578-596.
Tutin T.G. (1972) Lippia. In: Tutin T.G. & al. (eds.), Flora Europaea, volume 3. Cambridge University Press, Cambridge: 123.